One of the hottest book parties of the long, cold winter was the kickoff for Arianna Huffington’s new book, “Thrive,” tossed Monday night at the Fifth Avenue penthouse home of Steve Rattner and wife, Maureen White.

With a 150,000-copy first printing from the Harmony imprint of Random House — and a one-day rise to as high as No. 7 on the Amazon list — it appears destined for overnight best-seller status.

It certainly attracted an A-list crew of luminaries from politics, media and fashion.

On the political front, NYPD Commissioner William Bratton was seen posing with his predecessor, Ray Kelly. Also on hand was supermarket magnate John Catsimatidis, who lost in his campaign for the Republican nomination for New York City mayor last year.

Media star Katie Couric chatted with media mogul Barry Diller.

The night almost turned chilly for MSNBC “Morning Joe” talk show producer Louis Burgdorf, who revealed he had suffered a wardrobe malfunction when his pants split just prior to his arrival and he had to do a quick fix.

“I felt I couldn’t show up at Steve Rattner’s apartment with torn pants,” he said to Cosmopolitan Editor-in-Chief Joanna Coles and her husband, P.E.N. Americas President Peter Godwin, noting that he had stopped by J. Crew for a new pair of pants.

Godwin recalled that when he was first introduced to his future wife by a mutual friend, his friend had said, “You have to meet her — she’s the rudest woman in Britain!”

Barbara Walters was on the scene, but said she was saving her best stories about the Huffington Post founder for an interview the two were doing at the West Side Y on Tuesday night.

The Fly-By Award for quickest arrival — and departure — went to Norm Pearlstine, the chief content officer of Time Inc., who arrived with Fortune Managing Editor Andy Serwer but left before the toasts began.

Harvey Weinstein gamely deflected questions that he had a hand in prompting Cablevision Chairman James Dolan to postpone the Rockettes spring show at Radio City Music Hall.

“Yeah,” said Weinstein, “and I also brought in Phil Jackson as president of the Knicks and I am going to re-sign Carmelo Anthony.”

Glamour Editor-in-Chief Cindi Leive, in her toast, said that she learned from Arianna that you could turn off your cellphone for 45 minutes — and even for hours — “and the world would not come to an end.”

But turning it off for four days? “Only Arianna can do that,” Leive said.

Huffington said her book is about trying to find a new definition for success, after she worked herself to the point of exhaustion in 2007.

Mika Brzezinski, a co-host of the party as well as “Morning Joe,” opined that she felt she was an inspiration for Huffington to write the book, “because I was such a wreck” before learning to get more sleep.

Brzezinski asked Leive if the always-fashionable Glamour editor felt overworked to the point of being a wreck, to which Leive sniped, good-naturedly, “I was never a wreck.”